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DC/DC converter allows adjustable under-voltage lockout

Posted: 14 May 2010     Print Version  Bookmark and Share

Keywords:DC/DC converter  fault protection  power supply 

Linear Technology Corp. debuts the LT3581 current mode, fixed frequency step-up DC/DC converter that is suitable for applications with input sources ranging from a single-cell Li-Ion to automotive inputs. The converter packs integrated fault protection features for output shorts, input/output over-voltages and over-temperature conditions.

The LT3581 uses two integrated 42V switches—a 1.9A master switch and a 1.4A slave switch–which can be tied together for a total limit of 3.3A. The LT3581 operates from an input voltage range of 2.5V to 22V, with transient protection to 40V, making it suitable for applications with input sources ranging from a single-cell Li-Ion to automotive inputs. The LT3581 is ideal for many local power supply designs as it can be configured as either a boost, SEPIC or an inverting converter. The combination of a 4mm x 3mm DFN package (or MSOP-16E) and tiny externals ensures a very compact footprint while minimising solution cost.

The LT3581's low VCESAT switches, 0.25V (tied together at 2.75A), deliver efficiencies up to 88%. With both switches combined and from a 5V input, the LT3581 can deliver up to 830mA at 12V or 625mA at -12V. For high voltage outputs, the LT3581's slave switch enables high power charge pump topologies which are very efficient and require few external components. The LT3581's switching frequency can be programmed via a single resistor or synchronised to an external clock between 200kHz and 2.5MHz, minimising external component sizes and avoiding "noise critical" frequency bands. Under-voltage lockout is user adjustable for optimal system performance. A single feedback resistor sets the output voltage, minimising external components. Other features include external synchronisation capability and junction temperature monitoring.

The LT3581EDE is available in a 4mm x 3mm DFN-14 package, priced starting at $2.45 each for 1,000-piece quantities. The LT3581EMSE is also available in a thermally enhanced MSOP-16 package, priced starting at $2.55 each for 1,000 piece quantities. Industrial temperature (-40°C to 125°C) versions, the LT3581IDE and the LT3581IMSE, are also available from stock. Pricing starts at Rs.125.60 and Rs.130.68 ($2.72 and $2.83) each, respectively, for 1,000-piece quantities.

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